1. Field of the Invention
This invention relates to a field effect transistor with insulated gate electrode having a semiconductor body comprising an island-shaped first region of a first conductivity type which adjoins a first surface and surrounds a first zone of the second conductivity type likewise adjoining said first surface, and a second region of the second conductivity type which surrounds the first region and forms a pn junction therewith and adjoins the oppositely located second surface, a groove being provided in the first surface and extending through the first zone and the first region into the second region, the wall of which groove is coated with an electrically insulating layer on which a gate electrode is provided, the first zone and the second region being provided with connection conductors associated with the source and drain electrodes.
2. Description of the Prior Art
A field effect transistor of the kind described is disclosed in an article in Electronics, June 22, 1978, pp. 105-112.
With such a field effect transistor structure, rather large currents with power of more than 100 watts can be controlled at comparatively high frequency (up to a few hundred MHz).
In the known structure, in which the first region in which the channel is formed is a single region which consists of a usually diffused zone which, with the underlying second region, constitutes a surface-terminating pn junction, however, it is difficult to reach a very high breakdown voltage for said pn junction. In known transistors said breakdown voltage is of the order of at most a few hundred volts. This is due inter alia to the fact that said breakdown voltage is determined to a considerable extent by the edge curvature of the said pn junction and the unfavorable field distribution caused thereby and by surface states. Therefore, breakdown already occurs at comparatively low voltage at or near the surface.